Transdermal, or percutaneous, administration of pharmaceutical compounds is a known method of delivering drug compounds, or other agents, through the skin and into the human, or mammalian, circulatory system. The layer primarily responsible for inhibition of agents through the skin is the stratum corneum. The stratum corneum is a heterogeneous layer of flattened, relatively dry keratinised cells which limits the rate at which such agents can be administered therethrough, because of the chemical keratin-phospholipid complex it contains. Once a compound has penetrated the stratum corneum, which is approximately 15 microns thick, when dry, and expands to approximately 47 microns in thickness when fully hydrated, there remains no significant hindrance to penetration of the remaining epidermal layers. The remaining epithelial layers of the skin—the stratum granulosum, the stratum malpighii and the stratum germinativum—provide little, if any, resistance to the transmission of pharmaceutical compounds. Accordingly, once the stratum corneum has been penetrated, topically administered pharmaceutical agents are adsorbed through the lower epithelial layers and are able to enter into the circulatory system through the capillaries.
The prior art reports a variety of devices and methods for disrupting the stratum corneum for the purpose of delivering substances to the body. For example, breach of the stratum corneum may be achieved by puncturing as taught in U.S. Pat. No. 5,679,647 to Carson, et al. This patent teaches that narrow diameter tines, such as those found on devices used for tuberculin skin tests and allergy tests, can be coated with polynucleotides or oligonucleotides and used for delivery of such materials into the skin. The method of using such devices involves puncturing the skin with the types resulting in intracutaneous injection of the coated substance.
U.S. Pat. No. 5,003,987; U.S. Pat. No. 5,879,326; and U.S. Pat. No. 3,964,482 teach breaching the stratum corneum by abrasion.
It is, therefore, desirable to have an article of manufacture for transdermal drug delivery which can penetrate or abrade the stratum corneum using micron-sized projections, with a device for administering a pharmaceutical agent with precision and without causing undue intrusion into the lower epithelial layers, thereby minimizing patient discomfort or irritation.